Enhanced cleansing process for wafer handling implements

ABSTRACT

Methods are providing for cleansing contaminants from substrates, such as semiconductor wafer handling implements, and thereby reduce the incidence of contamination of semiconductor devices being assembled upon the semiconductor wafers. In one aspect of the invention, a substrate such as a semiconductor cassette or other semiconductor wafer handling implement, is inserted into a chamber that is substantially isolated from a surrounding environment. A pressurized, and optionally purified, cleansing medium is directed against at least one surface of the substrate to dislodge contaminants from the substrate surface. Dislodged contaminants are evacuated with negative pressure from the chamber. In a preferred aspect of the invention, the cleansing medium is an inert gas, such as nitrogen, and is applied to the substrate at a pressure from about 10 p.s.i. to about 100 or more p.s.i. The chamber can be provided with sidewalls define a convergent evacuation path that is in fluid communication with an exhaust stream, such as the exhaust stack of the manufacturing facility. A method of monitoring contaminant particle count and contaminant concentration which can be used to control the pressurized cleansing medium.

FIELD OF THE INVENTION

The invention relates to semiconductor manufacturing, and moreparticularly to the cleansing of wafer handling implements that are usedincident to the manufacture of semiconductor devices.

BACKGROUND OF THE INVENTION

The manufacture of semiconductor devices is a time consuming processthat requires high levels of cleanliness throughout the many phases ofthe manufacturing process. Many steps of manufacturing are conducted invarious classes of "clean rooms" having purified air flows to reduce theincidence of airborne particle contaminants to prescribed levels. Cleanrooms are typically designated in accordance with the number ofpermitted contaminants of a prescribed size per cubic foot of airspace.For example, much semiconductor manufacturing is presently conducted inClass 10 clean rooms, which have filtered air flows to permit no morethan 10 particles per cubic foot of up to 0.5μ in size. Nevertheless,wafers upon which the semiconductor devices are assembled can becomecontaminated, and therefore rendered defective, by contaminants that areintroduced at various process steps. For example, contamination canarise from incomplete cleansing of reagents from the wafer handlingapparatus, and the like. The presence of such contaminants can have acatastrophic impact on product yield, notwithstanding an otherwiseproper and complete formation of the semiconductor device. Moreover,although the wafers themselves can be properly cleansed of reagents andthe like that are used incident to various manufacturing steps, thewafer handling equipment, for a variety of reasons, may not becompletely cleansed of the reagents and may therefore serve as source ofwafer contamination for subsequent batches of wafers. Unfortunately, theprior art to date has not properly and fully addressed this latteraspect of contamination, and has instead sought to improve product yieldby addressing other aspects of semiconductor device manufacture.

Prior efforts to cleanse wafer handling implements have not beenentirely compatible with other aspects of device manufacture. Forexample, one known prior cleansing method within the clean room providedfor the use of a pressurized stream of air that was directed at a waferhandling implement such as a wafer cassette or boat. While thiscleansing practice was convenient and expedient, it had the unfortunateconsequence of creating turbulence in the airflow within the clean roomand introducing particulate contaminants into the clean room airstream,which resulted in increased particle contaminant concentrations at otherprocessing stations within the clean room. While the spread of airbornecontaminants was rectified by termination of this cleansing regimen, thecleansing regimen itself was not replaced. Therefore, the originalproblem associated with contaminated wafer handling implements haslargely remained uncorrected. Accordingly, there exists in thesemiconductor manufacturing industry a need for wafer handling cleansingmethods and apparatus which remove particulate contaminants from waferhandling implements such as wafer cassettes and the like prior to theircontact with wafers at various stages of manufacture. The provision ofsuch methods and apparatus could reasonably be expected to increaseproduct yield and therefore result in a corresponding increase inmanufacturing efficiency.

SUMMARY OF THE INVENTION

Methods and apparatus are providing for cleansing contaminants fromsubstrates, such as semiconductor wafer handling implements, and therebyreduce the incidence of contamination of semiconductor devices beingassembled upon the semiconductor wafers.

In one aspect of the invention, a substrate such as a semiconductorwafer cassette or other semiconductor wafer handling implement, isinserted into a processing chamber. A pressurized, and optionallypurified, cleansing medium is directed against at least one surface ofthe substrate to dislodge contaminants from the substrate surface.Dislodged contaminants are evacuated with negative pressure from thechamber, thereby reducing the concentration of contaminants on thesubstrate. In a preferred aspect of the invention, the cleansing mediumis an inert gas, such as nitrogen, which can be readily manufactured andsupplied at semiconductor manufacturing sites. The cleansing medium isapplied to the substrate at a pressure from about 10 p.s.i. to about 100or more p.s.i. Such pressures have been found to be particularlysuitable for removing contaminants of the type that are typicallyaccumulated on wafer handling equipment such as wafer cassettes. Thechamber can be provided with sidewalls that define a convergentevacuation path in fluid communication with an exhaust stream, such asthe exhaust stack of the manufacturing facility. The exhaust streampreferably has a flow rate of at least 10 c.f.m., and preferably atleast 75 c.f.m. or greater to ensure optimal evacuation of dislodgedcontaminants from the chamber. Exhaust stream flow rates of up to 500c.f.m. or more can also be provided to further enhance the cleansingprocess. The concentration of contaminants can be monitored byintroducing a particle monitor in the fluid flow path of the processingchamber or the exhaust conduit.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages of the present inventionwill become apparent to those skilled in the art from a reading of theaccompanying detailed description of the invention, taken together withthe accompanying drawings, in which:

FIG. 1 is a perspective view of a cleansing instrument in accordancewith the present invention;

FIG. 2 is a top elevation view of the device depicted in FIG. 1 with thedevice cover in an "open" position to illustrate details of the deviceprocessing chamber;

FIG. 3 is a rear view of the device depicted in FIG. 1;

FIG. 4 is a sectional view along the line 4--4 of FIG. 1;

FIG. 5 is a top elevation view of the device illustrated in FIG. 1 withthe device cover in a closed position.

FIG. 6 is a top view of an exemplary instrument control panel;

FIGS. 7-10 are flow diagrams of control logic for the methods andapparatus of the present invention; and

FIG. 11 is a flow diagram of a control processing regimen incident to acommand edit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the drawings, wherein like reference charactersrepresent corresponding parts throughout the various views, and withparticular reference to FIG. 1, there is depicted a substrate cleansingsystem in accordance with the teachings of the present invention,designated generally by reference character 20. The cleansing system 20is particularly useful for cleansing implements such as wafer cassettesand the like that are used in the handling and/or processing of wafersof semiconductor material incident to the manufacture of semiconductordevices. However, it is to be appreciated that the teachings of thepresent invention as described below can be used to cleanse implementsthat are used in other manufacturing processes.

The cleansing system 20 is comprised of a housing 24 that includesopposing front and rear panels 28 and 30, and side panels 32 and 34respectively. A control panel 36 is provided at the front panel 28 topermit for the entry of various user inputs and to display various typesof information relating to various aspects of device operation. Thecontrol panel includes visible indicia of system readiness, such as a"Power" light 38, which confirms placement of a power switch 40 in anappropriate position, such as an "on" or "standby" position. Aprocessing cycle of prescribed time duration can be initiated byappropriate manipulation of start selector 42. A cycle reset selector 44can be manipulated in an appropriate manner to ready the system forcommencement of a new processing cycle, as when conditions inhibitcommencement of a cycle following actuation of "start" selector 42. Aswill be more fully described below, the processing system monitorsvarious parameters to inhibit system operation in instances whereprescribed conditions are not satisfied. Such parameters can include, byway of non-limiting example, cleansing medium supply line pressure andexhaust vacuum pressure, one or more of which can be displayed in anappropriate manner on the control panel 36.

The housing 24 includes a base 48 that can be supported by legs 50 whichcan optionally be in the form of casters, self-leveling legs, or othersuitable supports. An upper surface 52 of the housing 24 includes acover or lid 56 that is pivotably connected to a remaining portion ofthe upper surface by suitable means, such as a hinge coupling (notshown). The cover 56 provides access to the interior of the cleansingsystem 20, and more particularly, to the system processing chamber 60.The processing chamber is defined by opposed sidewalls 64a-64d whichdefine a quadrilateral, a floor 68, and the inner surface 72 of the lid56. The sidewalls can optionally be provided with a curvilinear, asopposed to planar, configuration, as shown in the drawings.Alternatively, the processing chamber 60 can be defined by a structure,such as a circular or oval cylinder, having a curvilinear sidewall andfloor. Configuration of the processing chamber in any of the foregoingmanners provides a processing chamber that is substantially, althoughpreferably not completely, isolated from the environment surrounding thecleansing system 20 for reasons that will be more fully described below.

One or more of the chamber sidewalls 64, base 68 and the inner surface72 of the lid 56 can be formed from an electro-polished stainless steel,such as 304- or 316-grade stainless steel to facilitate the separationand removal of contaminants from a substrate received within the chamber60. Formation of these surfaces in this manner renders a hardened, flatsurface that is substantially devoid of surface irregularities, therebyfacilitating the passage of dislodged contaminants there along incidentto the cleansing process, as will be described in greater detail below.

An array of nozzles 76 is secured or otherwise mounted along the innersurface 72 of the lid 56 and is operable to deliver a pressurized streamof cleansing medium through nozzle apertures 78 to a substrate, such asa wafer cassette or other wafer handling implement, received within thecleansing chamber 60, as will be described in greater detail below. Oneor more of the nozzles 76 can optionally be arranged to direct acleansing medium stream that is angled with respect to the cleansingmedium streams emitted by the remaining nozzles. Moreover, one or moreof the nozzles can instead be coupled to a supply (not shown) of asuitable deionizing medium to deliver the deionizing medium to theprocessing chamber. The nozzles 76 can be repositioned along the lidinner surface 72 in an appropriate manner in accordance with suchfactors as the dimensions and configuration of the substrate to becleansed, the composition of the substrate, desired cleansing mediumspray pattern, and the like.

An access door 80 that is formed within one of the front (28), rear (30)or side (30/32) walls of the system, as shown in phantom in the drawing,can optionally be provided to afford supplemental access to theprocessing chamber 60. Alternatively, the door 80 can be provided inlieu of the hingedly securable lid 56 to simplify the cleansing systemmanufacturing and reduce associated expenses. Processing chamber accessfrom the side rather than the top can be beneficial in instances, suchas when handling quartz wafer cassettes and other contaminant sensitiveand/or heated or supercooled substrates, where tongs (not shown) andother special handling implements may be required. Access door 80 can behingedly coupled to a sidewall, such as sidewall 36, and is securable ina closed position by a conventional latch or other suitable lockingmechanism, such as that designated by reference character 84.

Further features of the cleansing system 20 are illustrated in FIG. 2. Apressurized flow of cleansing medium is supplied to the processingchamber 60 from an associated supply tank (not shown) or, morepreferably, by means of a supply line 88 that is connected to a facilityreservoir. The cleansing medium is preferably in the form of apressurized, and optionally purified, gaseous flow. Use of an inert gasis preferred so as to avoid interaction between the cleansing medium andthe contaminants carried by the substrate. As Nitrogen is used in otheraspects of semiconductor manufacturing and is available in highlypurified concentrations, its use as a cleansing medium is particularlyadvantageous. However, other appropriate cleansing mediums, such aspurified, dehydrated air and other fluids that are non-reactive withcontaminants that may be present on a given substrate, can besubstituted for the inert gas.

The cleansing medium is conveyed from its inlet connection 92 (FIG. 3)along the rear panel 30 to the nozzle array 76 (FIG. 1) through aninternal conduit 96. Delivery of the cleansing medium into the conduit96 is regulated by an appropriate flow control device, such as solenoid98 or other precision valving device. Conduit 96 is coupled to anexternal, flexible hose 100 through appropriate fittings, such as highpressure threaded fittings 102, 104 that are respectively mounted to therear wall 30 and lid 56 of the cleansing system 20. The ends of the hose100 are provided with fittings 103 and 105 that are configuredcomplementary to fittings 102 and 104 to securely engage the fittings103 & 105. Electrical power is supplied by a conventional 110 volt powerline 106 or by other suitable sources of electrical power. Suppliedelectrical power is managed and processed in an appropriate manner toprovide for powering of the various system relays, circuits and controlapparatus, as well as the control panel 36.

With reference to FIG. 2, there is illustrated a substrate 110 in theform of a quartz wafer cassette that is received within the processingchamber 60 of the cleansing system. While a quartz wafer cassette isdiscussed in the following description, it is to be understood that theprinciples of the invention are equally applicable to non-quartz wafercassettes, as well as to other types of wafer handling and other,non-wafer handling implements. The wafer cassette 110 includes pluralityof wafer supports 112 that are arranged parallel to one another. Eachsupport 112 includes a plurality of transversely extending slots 114,each of which is dimensioned to receive a wafer of semiconductormaterial therein. In the illustrated wafer cassette 110, the number ofwafer slots 114 has been greatly reduced, and the spatial dimensions ofthe slots have been exaggerated with respect to the dimensions andstructure of conventional quartz wafer cassettes for reasons of clarity.The wafer cassette 110 is supported in the processing chamber 60 by amounting rack 118 that is dimensioned and configured to support thesubstrate 110 above the processing chamber floor 68. When quartzcassettes are to be cleansed, the rack 118 is preferably formed fromvarious resins or polytetrafluoroethylenes ("PTFE's") to avoid reactionwith, or retention of, contaminants introduced into the processingchamber 60 by a substrate to be cleansed. When polypropylene and othernon-quartz implements are to be cleansed, the rack 118 can be formedfrom an electro-polished stainless steel, such as 304- or 316- gradestainless steel.

As is illustrated more clearly in FIG. 4, the processing chamber base 68is preferably sloped downwardly and away from the substrate 110 so as tofacilitate conveyance of dislodged contaminants from the processingchamber 60 and into the exhaust stack (not shown) of the manufacturingfacility. Connection to the exhaust stack is through an exhaust conduit120 that extends from the rear wall 30 of the system. Alternatively, theexhaust conduit 120 can be positioned so as to extend from the chamberfloor 68 to more fully utilize the effects of gravity. Exhaust stacksare typically continuously operable in semiconductor manufacturingfacilities and generally exhibit flow rates of between 25 and 1,000c.f.m. in accordance with, among other factors, the demands associatedwith various process steps. It is to be appreciated that connection tothe exhaust stack creates a negative pressure within the processingchamber 60 which, in and of itself, tends to draw dislodged contaminantsaway from the substrate 110 and into the exhaust stack through theexhaust conduit 120. A suitable particle monitor 122, such as an in-situparticle monitor or residual gas analyzer, can be coupled to exhaustconduit 120 to provide feedback via lead 123 in an appropriate mannerregarding the level of contaminants in the fluid flow evacuated from theprocessing chamber. Depending on the extent of negative pressuregenerated by such a connection, an inlet or vent 124, as shown in FIG.5, can optionally be provided to facilitate the ease with which thecover 56 can be elevated from the closed position shown in FIG. 5 to theopen position shown in FIG. 1. Alternatively, an iris, shutter or othersuitable valving device can be provided at the exhaust conduit toselectively regulate communication between the processing chamber 60 andthe exhaust stock. However, provision of vent 124 is desirable, for itallows for continuous cleansing of the processing chamber with ambientclean room air. Manipulation of the lid 56 can be further facilitatedthrough provision of a handle 128 that can be connected to the lid orincorporated therein in a conventional manner.

Operational safeguards, such as a lid interlock switch 130 and exhaustinterlock 134, as depicted in FIG. 3, can optionally be provided tofacilitate safe operation of the processing system 20. For example, thelid interlock 130 can be operable to maintain the lid 56 in a closedposition, as shown in FIG. 3, once the cleansing cycle has beeninitiated, as by depression of the start button 44 (FIG. 1), as well asto communicate with solenoid 98 to inhibit the release of pressurizedcleansing fluid to the nozzles 76 in the absence of engagement of theinterlock 130. Likewise, the exhaust interlock 134, which can been inthe form of a diaphragm-type valve, is operable to sense negativepressure through the exhaust conduit 120 and to inhibit operation of thesystem in instances where the sensed negative pressure is below apredetermined threshold value.

System Operation

A detailed description of the operation of the cleansing system 20 ofthe present invention will now be provided in connection with thecleansing of a substrate 110 in the form of a semiconductor wafercassette, although it is to be appreciated and understood that thefollowing description is likewise applicable for the cleansing ofmultiple and/or various other substrates, such as other types ofsemiconductor wafer handling implements, as well as other types of itemsfor which cleansing is desirable.

With particular reference to FIGS. 1 and 2 of the drawings, a wafercassette 110 is inserted into the processing chamber 60 for cleansingprior to use with a semiconductor wafer (not shown) at any of a varietyof stages of wafer processing. The wafer cassette 110 is positioned onthe rack 118 that is received within the processing chamber 60 so as tosupport the cassette 110 above the angled processing chamber floor 68.The rack 118 can optionally be configured to retainably engage thecassette 110 and to position the cassette in a predetermined orientationwithin the processing chamber 60 and with respect to the one or morerows of cleansing nozzles 76 that are provided along the inner surfaceof the lid 56.

Once the cassette 110 is received within the processing chamber 60 inthe foregoing manner, the lid 56 is displaced from the open position(FIG. 1) to the closed position illustrated in FIG. 4, and theprocessing system 20 is turned on, as can be accomplished by togglingthe switch 40 (FIG. 1) from the "off" position to the "on" position.Displacement of the power switch in the foregoing manner illuminatespower indicator light 38, thereby confirming the delivery of power tothe system. Safety interlock 130 (FIG. 3) generates appropriate signalinput to confirm lid closure. In addition, appropriate signal input isprovided by the exhaust interlock sensor 134, which is operable toprovide "go\no go" status with respect to negative pressure supplied tothe processing chamber 60 through the exhaust conduit 120. Such negativepressure is obtained from the connection of the exhaust conduit 120 tothe exhaust stack of the manufacturing facility, as has been describedpreviously. In a preferred aspect of the invention, commencement of acleansing cycle can be accomplished only after receipt at the controlpanel 36 of favorable signal output from the lid interlock and exhaustinterlock sensors 130 & 134, respectively, so as to inhibit operation ofthe cleansing system outside of prescribed operational parameters, suchas incomplete lid closure and insufficient exhaust flow rate.

The cleansing cycle is started by depressing the start button 44 (FIG.1), which initiates the release of fluid conduit solenoid valve 98,thereby freeing the flow of cleansing medium to the array of nozzles 76.While a variety of cleansing mediums can be implemented with thepractice of the present invention, in a preferred aspect of theinvention, the cleansing medium is gaseous nitrogen, which is typicallyavailable in semiconductor wafer manufacturing facilities in highpurity. Such nitrogen is typically supplied at a line pressure of about100 p.s.i. However, the nitrogen is preferably delivered to the nozzles76 at a pressure of from about 10-100 p.s.i. in accordance with thestructure and configuration of the nozzle outlets 78 and the number andarray of nozzles. Dynamic pressure at the nozzle can be sensed in aconventional manner and indicated at the control panel pressure gauge46. Alternatively, the gauge 46 can be connected to the supply line ofthe cleansing medium to provide an indication of static supply linepressure. Simultaneous displays of both of the foregoing pressures canalso be provided.

The cleansing cycle is defined by a predetermined time interval, whichis optimally between about 30-120 sec. at a nozzle pressure of betweenabout 30 and 75 p.s.i.

Tables 1 and 2 provide measured data that was obtained prior to andfollowing processing of various types of wafer cassettes in accordancewith the present invention. Table 1 provides data that was obtained withrespect to three types of wafer cassettes: carrier cassettes, ovencassettes, and etch cassettes. Table 2 5provides data that specificallyrelates to the cleansing of etching cassettes. Carrier cassettes providefor the transportation of wafers between processing sites, at which thewafers are off-loaded to other types of cassettes, such as ovencassettes and etch cassettes that are designed and fabricated forspecific types of processing. For example, furnace cassettes aretypically fabricated from quartz so as to withstand high temperatureprocessing in furnaces at temperatures in excess of 800° C. Etchcassettes are formed from various acid resistant materials, such ascertain plastics and members of the polytetrafluoroethylene ("PTFE")family. All of the wafer cassettes included in Tables 1 and 2 wereprocessed under the following conditions:

Cleansing medium line pressure: 100 p.s.i.

Cycle duration: 30 seconds

Cleansing medium: gaseous nitrogen

Exhaust stack flow: 25-150 c.f.m.

                  TABLE 1                                                         ______________________________________                                        Particle Count                                                                Cassette Type/No.                                                             Processing      Before Processing                                                                          After                                            ______________________________________                                        Carrier/1        5           1                                                Carrier/2       19           11                                               Carrier/3       195          0                                                Carrier/4       15           8                                                Carrier/5       88           2                                                Carrier/6       27           12                                               Carrier/7       56           19                                               Carrier/8       29           40                                               Carrier/9       10           4                                                Carrier/10      73           1                                                Carrier/11      33           4                                                Oven/1          362          75                                               Oven/2          239          17                                               Oven/3          20           2                                                Oven/4          176          0                                                Oven/5          176          0                                                Oven/6          41           0                                                Oven/7          89           0                                                Oven/8           7           0                                                Etch/1           4           0                                                Etch/2           2           1                                                Etch/3          12           1                                                Etch/4          3536         853                                              Etch/5           3           3                                                Etch/6          1533         241                                              Etch/7          2367         449                                              ______________________________________                                         Average PreProcessing Particle Count: 351.8                                   Average PostProcessing Particle Count: 67.1                                   % Particle Reduction: 80.9                                               

                  TABLE 2                                                         ______________________________________                                        Particle Count                                                                Cassette Type/No.                                                             Processing      Before Processing                                                                          After                                            ______________________________________                                        Etch/1          290           49                                              Etch/2          207           24                                              Etch/3          489           31                                              Etch/4           18           2                                               Etch/5          660           79                                              Etch/6          2203         143                                              Etch/7          631          222                                              Etch/8          193          138                                              Etch/9          1319         170                                              Etch/10         1494         177                                              ______________________________________                                         Average PreProcessing Particle Count: 750                                     Average PostProcessing Particle Count: 103.5                                  % Particle Reduction: 86.7%                                              

The empirical data obtained from the foregoing evaluations indicated animprovement in wafer cassette cleanliness of between about 80%-about90%. Accordingly, wafers transported by the various cassettes that werecleansed in the foregoing manner were subjected to 80-90% fewercontaminants than to which they otherwise would have been subjected.

The foregoing cleansing process provided a contaminant reduction thatwas far greater than ever anticipated by the inventors. In relatedtests, the foregoing cleansing practices resulted in a yield improvementfor short flow lots of between 5 and 11%, even when "best" practices,where cost was of secondary consideration, were implemented.

In a further aspect of the invention, the processing system 20 of thepresent invention is provided with an electronic control system that ispreferably of a type which is operable to monitor and control a varietyof system performance parameters, as will be described in greater detailbelow. Included among the performance parameters is a pulsing regimenfor the application of cleansing medium, as will be also be described indetail below.

An electronic control panel in accordance with the teachings of thepresent invention is denoted generally by reference number 150 in FIG. 6and can be added to the system 20 to augment or replace panel 36illustrated in FIG. 1. The control panel can be in the form of areconfigurable commercial-grade operator interface unit, such as aNematron Series 200C PLC graphics workstation, manufactured by NematronCorporation of Ann Arbor, Mich. The control panel can be configured inthe manner depicted in FIG. 6 to include a status display screen 154, aplurality of pre-programmed functionality keys 156, a plurality ofalpha-numeric data input keys 158, a reset/abort key 160, and a cyclestart key 162. Each of the pre-programmed functionality keys 156 can beprovided with discrete processing regimens in accordance with suchfactors, for example, as the type of implement to be cleansed, asdifferent implements by virtue of their use environment, structuralconfiguration and the like can require different cleansing regimens. Aswill be discussed below, cleansing regimens can differ by havingdifferent time periods of cleansing medium application and cleansingmedium application pressure, as well as pulse frequency and pulseduration of cleansing medium application, and the "settle time" betweenadjacent pulses.

The display screen 154 is preferably an alpha-numeric display that iscapable of depicting various operational status parameters, such aserror codes, data entry from selection of one or more of the input keys158, elapsed time, particle count (when the processing system isconnected to optional particle monitor 122 (FIG. 4), program entry/editcommands, and the like. With particular reference to the data entry keys158, such keys are generally comprised of the following types: (a)multi-function alpha-numeric input keys 164-182 which respectivelycorrespond to numbered keys 0-9; (b) multi-function program edit andstore keys 184 & 186; (c) multi-function access keys 188, 190 & 192 foraccessing various of the functions (such as alpha-numeric and arithmeticfunctions) embedded in input keys 164-182; (d) specific processingfunction keys 194 ("Time"), 196 ("Cycle/Count"), 198 ("Pulse Time"), and200 ("Settle Time"); and (e) system data/access/function entry key 202("Enter").

As will be more fully described below, functionality of the processingsystem can be modified in accordance with entry of specific commandsthat are associated with corresponding control panel keys 156-202. Forexample, the duration of a processing cycle can be selected bydepressing "Time" key 194, selecting one or more of the keys 164-182corresponding to the desired time period (usually in seconds), and thendepressing "Enter" key 202. A pre-existing program can be selected bydepressing one of the pre-programmed keys 156 and depressing "Enter" key202. Processing until a desired particle count is attained within theprocessing chamber 60 can be accomplished by depressing "Cycle/Count"key 196 followed by one or more of the keys 164-182 which correspond tothe desired contaminant level, and depressing "Enter" key 202. This willprovide for processing until attainment of output from particle monitor122 indicative of the selected particle count. The key designated "PulseTime" 198 allows for entry of a desired time period for application of acleansing medium pulse. The key designated "Settle Time" 200 allows forentry of a time period between pulses, during which cleansing medium isnot expelled into the processing chamber 60. Processing for apredetermined number of cleansing medium application cycles can beselected by depressing "Cycle/Count" key 196 an appropriate number oftimes, such as two, followed by entry of the specific number of cyclesvia selection of one or more of the keys 164-186, followed (optionally)by selection of "Pulse Time" key 198 in the manner set forth above.

With reference to FIGS. 7-10, there are depicted flow diagrams of thelogic steps employed by the control panel 150 and related powersupplies, relays, valving hardware and the like in accordance with theteachings of the present invention. With particular reference to FIG. 7,there is depicted a high level diagram of control panel operationfollowing powering-up of the system and running of self-diagnostics in amanner well known to practitioners in the relevant art. Uponinitialization, the status of the system is indicated in screen display154 (FIG. 6), as indicated by block 210, and the system is operable tomonitor selection of various inputs, as indicated by decision blocks212, 214, 216 and 218. While the following description addresses thedecision blocks 212-218 in a sequential manner, it is to be understoodthat such a sequential process is not necessarily indicative of themanner in which software associated with the control panel implementsthis interrogative process. For example, the following interrogativeprocess can be accomplished substantially simultaneously, orsequentially, but in a different order from that set forth below, as isknown to persons of ordinary skill in the programming art.

Decision block 212 relates to whether or not the "START" key 162 hasbeen depressed, the selection of which will direct the control panel toimplement the last selected program entry, as indicated by block 220. Ininstances where the "START" key has not been depressed at a given pointin time, the control system is operable to evaluate selection of otherinputs 214-218. For example, block 214 relates to whether apro-programmed function key 156 has been selected, in which case thecontrol panel recalls the selected program from associated memory andexecutes the recited program steps, as indicated by block 222. Suchpre-programmed functions can include, by way of non-limiting example,programs directing the application of cleansing medium in adiscontinuous (i.e., pulsed) manner with prescribed pulse durations and"settle times" between pulses, for a prescribed time interval or until apredetermined particle count has been attained. As will be discussed infurther detail below, it can be desirable to select from a variety ofdifferent cleansing medium application regimens in order to implementcleansing of different types of substrates, such as semiconductor waferetch, photoresist and carrier cassettes, cassette-related handlingimplements, and the like. In the absence of selection of either of the"START" or "PRE-PROGRAMMED CYCLE SELECT" functions, the control panel150 is operable to evaluate selection of "EDIT" key 184, as indicated byblock 216. In instances where "EDIT" has been selected, the associatedprogram parameters, such as any one or more of pulse/settle times, cycleduration, number of pulse applications per cycle, particle count, andthe like, will be recalled from associated program memory (not shown)and displayed either simultaneously or sequentially on the controldisplay screen 154 for review and/or edit, as indicated at block 224.Editing can be accomplished in any of a variety of conventional manners,as by advancing a screen cursor to a desired parameter entry andoverwriting the existing entry with a new entry. Revised programs can bestored by any of a variety of suitable, conventional storage regimens,such as selection of "STORE" key 186 and designation of an appropriaterecallable storage address in memory. In the absence of selection of anyof the foregoing "START" (block 212), "PRE-PROGRAMMED CYCLE" (block 214)or "EDIT" (block 216) functions, the control panel is operable toevaluate selection of an appropriate keypad entry allowing fordownloading of a program from a host computer (block 218) with which thecontrol panel can be selectively associated in a conventional manner. Insuch instances, the program is received at an appropriate address incontrol memory (block 226) for subsequent recall and/or use in themanner described above.

Details of the program logic that is associated with the pulseprocessing of a substrate are illustrated in FIG. 8. With reference tothe drawing, the particle counter 122 (FIG. 4) is reset and startedfollowing entry of the appropriate processing parameters, such asprocess time, pulse duration/settle times, number of pulse cycles, andthe like, and the timer is started, as indicated by blocks 230 and 232,respectively. Cleansing medium is released to the nozzles 76, as byactuating solenoid/valve 98 (FIG. 3) to open inlet conduit 96 (block234), until the first to occur of an external interruption, such asdepression of "RESET/ABORT" key 160 (block 236) or passage of theselected or programmed cleansing medium application time (block 238). Ininstances where the "RESET/ABORT" key has been depressed, the particlecount is terminated (block 240), all timers and cycle counters are reset(block 242), and the control panel returns to the main screen display,as indicated by block 244.

In the absence of an interruption, such as depression of "RESET/ABORT"key 160, or the passage of the prescribed pulse interval (typicallymeasured in seconds or fractions of a second), appropriate signal inputis directed to solenoid/valve 98 to remain in the "open" position so asto permit the flow of pressurized cleansing medium to the applicatornozzles 76. Upon passage of the prescribed pulse interval, appropriatesignal input generated by the control panel 150 to direct closure ofsolenoid/valve 98 so as to terminate application of cleansing medium, asindicated by block 246. In the absence of external interruption, such asdepression of "RESET/ABORT" key 160 (block 248), the prescribed settletime is permitted to pass, as indicated by block 250. The control systemagain monitors for the depression of "RESET/ABORT" key 160 (block 252)and, in the absence of such, evaluates whether or not the prescribednumber of pulse/settle cycles has been completed, as shown by block 254.In the absence of completion of the prescribed number of pulses, a cyclecounter is incremented (block 256), the timer is re-started, and theforegoing program flow is repeated. If the prescribed number ofpulse/settle cycles has been completed, the particle counter isterminated, as indicated by block 240, and the ensuing actionsreferenced in blocks 242 & 244 are implemented in the manner describedabove. Actuation of "RESET/ABORT" key 160 following passage of theprescribed settle time (block 250) directs stoppage of the particlecounter (block 240) and processing in accordance with blocks 242 & 244as set forth above.

The foregoing protocol for a pulse cleansing regimen is applicable to awide range of cleansing cycles, during which cleansing media can beapplied for periods as brief as fractions of seconds to periods of 30 ormore seconds. However, for some substrates, it can be more desirable toapply relatively short duration pulses in rapid succession to effectcleansing, as some contaminants are more responsive to the initial,high-pressure blast of the cleansing medium than to the prolongedapplication of a cleansing medium stream. It is for this reason that itis preferable to provide for individual setting of pulse application andsettle times. The settle time can be related to the pulse time by afractional or whole number increment. Typical relationships betweenpulse application and settle times can range, for example, from 1:1 to1:4 (i.e., settle time is up to about four times the duration of thepulse application time). Moreover, for a given program cycle, it ispossible to vary one or both of the pulse application and settle times,as well as the ratio between these time values. It is further possibleto institute a regimen of pulse "sweeping" within the processing chamberby applying cleansing medium in a sequential manner to discrete groupsof nozzles 76 to effectuate the application of cleansing medium from oneside of the chamber to the other side. Alternatively, the cleansingmedium can be applied to discrete groups of nozzles 76 in anon-progressive manner in an effort to increase turbulence within theprocessing chamber 60.

As has been noted above, nozzles 76 can be arranged into discretegroups, such as the three groups 260a-260c indicated in phantom inFIG. 1. When the nozzles are arranged into a multitude of groups, eachgroup is to be supplied with cleansing medium independently of thenozzles constituting the other nozzle groups. One arrangement forimplementing such independent delivery is illustrated in FIG. 9, inwhich the fluid inlet 96 upstream of the flow controller/solenoid 98(i.e., between the flow controller 98 and nozzles 76) is provided with aflow diverter unit, indicated generally by reference numeral 270, towhich the inlet 96 can be coupled by appropriate fluid couplings, suchas threaded connector 273 which, together with the flow diverter unit270, are provided with mutually engageable threaded surfaces 273a and273b.

The diverter unit 270 includes a flow divider plate 272 which providesfor the partitioning of the incoming supply of cleansing medium into amultitude of discrete sub-flows, of which three are illustrated. It isto be appreciated that a greater or lesser number of sub-flows can becreated by the divider plate 272 or other equivalent structures. A fluidline 274 extends from the divider plate 272 to a corresponding flowcontrol device 276, such as a solenoid or other high pressure flowcontrol device. Each of the flow control devices can be independentlycontrollable by the controller 150 in a manner well known in the art soas to separately bias the controllers 276 between "open" and "closed"positions. An outlet line 278 extends from each flow controller 276 andextends to an outlet 280 of the diverter, where the outlet lines areconnected through appropriate coupling apparatus 284 to correspondingfluid delivery lines 286 received within the inlet conduit 96 fordelivery to their corresponding group of nozzles 260a-260c. Appropriatefluid distribution apparatus can be provided in the lid to divide theincoming fluid flows from delivery lines 282 to the plurality of nozzles76 constituting the nozzle group.

With reference to FIG. 10, there is depicted the process logic employedby controller 150 to implement a pre-programmed processing regimen, ascan be implemented by selecting one of the control pre-programmed keys156 (FIG. 6). The selected program is presumed for the followingdiscussion to provide for a predetermined cleansing medium pulseapplication regimen having preestablished pulse application and settletimes that have been pre-programmed by a supplier or system user in themanner set forth above. A predetermined number of pulseapplication/settle cycles is preferably established in the program inorder to prevent continuous operation of the cleansing system ininstances where it is not possible to attain the set level ofcleanliness for a given substrate.

Upon selection of the appropriate key 156 and selection of "START"button 162, the clock timer and particle counter are started, as shownby blocks 290 & 292. Cleansing medium is released (block 294) by propermanipulation of flow controller 98 (and optionally any one or more ofauxiliary controllers 276), as elapsed time is monitored (block 296). Ininstances where the elapsed time has not attained the preestablished orprogram "set" time, the controller 150 is operable to continue with itscount of particles, as indicated by block 298. The controller monitorsthe number of pulse application cycles (block 300) and, for so long asthe elapsed time has not attained the "set" time (block 296), and theparticle count has not attained the preestablished count limit (block298), the controller continues to direct signal output to the flowcontroller 98 (and optionally controllers 276 (FIG. 9)) to provide forthe continued release of cleansing medium. In instances where the "set"time (block 296), preestablished particle count (block 298) or cyclecount (block 300) has been attained, the controller 150 directs the flowcontroller/solenoid 98 to close so as to terminate application ofcleansing medium (block 302). The particle counter terminates its count,optionally displays on screen 154 the attained count or other messageindicative of completion of a processing cycle, and resets (block 304),and the controller returns to its main screen display (block 306).

FIG. 11 depicts the controller processing regimen for implementation ofa program edit. Program editing can be initiated by, for example,selecting controller "EDIT" key 184 followed selection of one of thepre-programmed keys 156 so as to edit a cleansing regimen that is storedin appropriate controller addressable memory, as indicated by block 320.Selection of a key 156 results in the display of the variety ofparameters that constitute the programmed cleansing cycle. Suchparameters can include, for example, the following: (1) process time;(2) individual cleansing cycle time; (3) pulse application time; (4)settle time; (5) number of cleansing cycles; and (6) lower limit ofparticle count. Following display of the program parameters, thecontroller is operable to determine whether or not "RESET/ABORT" key 160has been depressed, as indicated by block 322. "RESET/ABORT" is selectedin instances, for example, where the incorrect pre-programmed key 156has been selected or the user does not desire to change any of theprogram parameters constituting the program. In instances where of"RESET/ABORT" key 160 has been depressed, the program returns to "idle"status, awaiting further input. In the absence of a "RESET" entry, theprogram awaits receipt of program parameter changes, as indicated bydecision block 324, and selection of "STORE" key 186 to implementprogram storage (block 326), after which an appropriate program storageconfirmation can be generated, as indicated by block 328. In the absenceof selection of "STORE" key 186 following the entry of program parameterchanges and the passage of a prescribed time interval, the program willgenerate an appropriate screen prompt (block 330) and await anappropriate user response. In the absence of selection of "RESET" (block332), as could occur in instances where the user determined not toimplement the keyed-in parameter changes, and the passage of apredetermined "lapse" time interval (block 334), the program returns toa "wait state" for entry of the "STORE" command at block 326. In theevent of "RESET" selection or lapsing of a predetermined time interval,the program returns to the "wait state" to await entry of an appropriatecommand, as indicated at block 320.

Although the present invention and its advantages have been described inconnection with the preferred embodiments, it is to be understood andappreciated that various changes, substitutions and modifications can bemade herein without departing from the scope and spirit of the inventionas defined by the accompanying claims. For example, it may be desirableto provide an automated control to the processing system to permit entryof a user variable processing time to custom tailor a processing cyclein accordance with the level of cleanliness and the type of substrate tobe cleansed. Alternatively, the processing system could be modified toobtain particle count data from the processing chamber exhaust to permitfor processing until a desired level of exhaust air cleanliness isattained, in which case the processing cycle would not be timedependent. Moreover, the cleansing medium could optionally be applied ina discontinuous manner during the course of a processing cycle,regardless of the processing cycle parameter that is employed (i.e.,particle count or elapsed time).

What is claimed:
 1. A method for cleansing a substrate, comprising thesteps of:applying a pressurized stream of a cleansing medium against atleast one surface of a substrate; evacuating with negative pressure theapplied cleansing medium; monitoring at least one of a contaminantparticle count and a contaminant concentration; and applying saidpressurized stream until at least one of a predetermined contaminantparticle count or concentration is attained.
 2. The method according toclaim 1, wherein said cleansing medium is an inert gas.
 3. The methodaccording to claim 1, wherein said cleansing medium is applied at apressure of from about 10 p.s.i. to about 100 p.s.i.
 4. The methodaccording to claim 1, further comprising the step of inserting saidsubstrate in a receptacle chamber, said receptacle chamber beingprovided with sidewalls that include surfaces that are arranged along atleast two intersecting planes.
 5. The method according to claim 4,wherein said substrate is received by a substrate support positionedwithin said receptacle chamber.
 6. The method according to claim 4,further comprising the step of drawing ambient air into said receptaclechamber.
 7. The method according to claim 1, wherein said substrate is asemiconductor wafer handling implement and said cleansing medium is agaseous flow.
 8. The method according to claim 1, further comprising thestep of dislodging contaminants with said pressurized stream from saidsubstrate.
 9. A method for cleansing a substrate, comprising the stepsof:providing a cleansing medium stream and directing said stream at asubstrate through a plurality of orifices; controlling through whichorifices said cleansing medium is released; and evacuating with negativepressure said cleansing medium directed against said substrate.
 10. Themethod according to claim 9, further comprising the step of pulsingapplication of said pressurized stream and selecting at least one of apulse frequency and a pulse duration of application of said cleansingmedium stream.
 11. The method according to claim 9, wherein saidorifices are arranged so as to release said cleansing medium along atleast a single plane.
 12. The method according to claim 9, wherein saidorifices are arranged in discrete, independently operable zones.
 13. Themethod according to claim 9, wherein said cleansing medium is an inertgas.
 14. The method according to claim 9, wherein said cleansing mediumis applied at a pressure of from about 10 p.s.i. to about 100 p.s.i. 15.The method according to claim 9, wherein the receptacle chamber isprovided with sidewalls that include surfaces that are arranged along atleast two intersecting planes.
 16. The method according to claim 9,wherein said cleansing medium is directed into at least one nozzle forapplication to the substrate to be cleansed.
 17. The method according toclaim 16, wherein the substrate is a wafer cassette having at least onewafer-receiving slot and said nozzle is operable to direct saidcleansing medium into said wafer slot.
 18. The method according to claim9, further comprising the step of measuring contaminant concentrationwith said chamber.
 19. A method for cleansing a substrate, comprisingthe steps of:providing a cleansing medium stream and directing saidstream at a substrate through a plurality of orifices; controllingthrough which orifices said cleansing medium is released; evacuatingwith negative pressure said cleansing medium directed against saidsubstrate; and monitoring a contaminant concentration level in saidevacuated cleansing medium.